Process and apparatus for heartworm microfilariae detection

Abstract

Methods and apparatus are already in use in the field of veterinary medicine for detecting microfilariae of heartworm in blood, comprising lysing blood samples to destroy corpuscular components, filtering the lysed samples on microporous transparent filters, staining any microfilariae on the filter, and observing the stained microfilariae under a microscope. The present invention simplifies and improves upon the older practices by providing a premix of lysing solution and staining dye, in a disposable vial, and a disposable filtrate vial surmounted by disposable filter cap holding a microporous filter element. The blood sample is injected into the premix for simultaneous lysing and staining, transferred to the filter cap for filtration and the filter element transferred to a microscope slide for observation.

What I claim is 
     
       1. An improved process for the detection of microfilariae in blood, comprising in combination, (a) the preparation of a solution mixture containing at least one dye suitable for staining said microfilariae, and components suitable for causing lysis of the blood, said dye and said components being mutually compatible,   (b) adding a blood sample to said solution mixture and holding briefly to allow lysis to take place and staining of said microfilariae,   (c) filtering the stained, lysed sample on a microporous filter and   (d) transferring the filter to a microscope slide for examination for stained microfilariae.   
     
     
       2. The process of claim 1, in which the said blood sample (a) previously obtained by drawing into a syringe,   (b) is ejected into said solution mixture, and   (c) after having been held briefly the stained lysed sample is transferred for filtration on said microporous filter,   
     
     
       3. The process of claim 1, in which the said blood sample (a) previously obtained by drawing into a syringe with needle,   (b) is ejected through said needle into said solution mixture,   (c) after having been held briefly the stained, lysed sample is withdrawn through said needle into said syringe and   (d) is then ejected from said syringe for filtration on said microporous filter,   
     
     
       4. The process of claim 1, in which the solution mixture comprises aqueous formaldehyde of 0.5-5% strength by weight, together with a staining dye for microfilariae stable in formaldehyde. 
     
     
       5. The process of claim 4, in which said staining dye is at least one of gentian violet, methylene blue, trypan blue, or bromcresol purple. 
     
     
       6. The process of claim 1, in which the solution mixture is employed in about 1 to 5 times the volume of the blood sample. 
     
     
       7. An apparatus for carrying out the detection of microfilariae in a blood sample, comprising in cooperative combination (a) a standard hypodermic syringe with male end and a needle with female socket for drawing sample of blood from an animal under test,   (b) a first vial containing a solution mixture of dye suitable for staining said microfilariae, together with components suitable for causing lysis of the blood, said dye and said components being mutually compatible, said first vial having a cover means,   (c) a second vial for receiving a filtrate   (d) a filter-media-holding cover for said second vial, operable to facilitate removal of said filter media, and having an inlet.   (e) said inlet being adapted to enable transfer of any fluid without leaking from said first vial to said filter media-holding cover.   
     
     
       8. The apparatus as in claim 7, in which the said inlet means has a female taper adapted to cooperate with the male end of the hypodermic syringe. 
     
     
       9. The apparatus of claim 7, in which the cover means of the first vial has a male protrusion adapted to cooperate with a female taper of the inlet of the said filter-media-holding cover.